1. Field of the Invention
The present invention relates to a liquid crystal device and a method for producing the same. More particularly, the present invention relates to a sealing of a liquid crystal injection inlet in the liquid crystal device using a ferroelectric liquid crystal. Further, the present invention relates to a method for producing a liquid crystal device which can maintain substrates at a constant distance.
2. Description of the Related Art
Recently, a display unit using a liquid crystal has been noted, but in the case where an inexpensive glass substrate or a resin substrate (plastic substrate) is used, it is difficult to enlarge a display area of a liquid crystal display unit. In particular, where the display unit using a nematic liquid crystal is vertically used, deflection occurs in substrates due to a weight of the display unit, and a liquid crystal cell thickness changes because the liquid crystal gathers toward the bottom of the cell due to gravity. As a result, display properties deteriorates. On the other hand, in order to realize a high-speed response of the liquid crystal display unit, a method is considered, which uses a high-speed responsive material such as a ferroelectric liquid crystal as a liquid crystal material.
However, even in the case, for example, where a high-speed response of a liquid crystal display unit is realized by using the ferroelectric liquid crystal as a liquid crystal material, the problem still exists that it is difficult to enlarge a display area of the display unit. The reason for the above is that since the ferroelectric liquid crystal has a layer structure, this layer structure is broken by deformation of substrates, resulting in disturbance on display. This problem is not limited to only in use of the ferroelectric liquid crystal, and basically similar problems occur even in the case of using many other liquid crystal materials.
Further, where such the ferroelectric liquid crystal is used, a problem occurs in a sealing stage after injecting the liquid crystal into a liquid crystal cell. The term "sealing" used herein means that after injecting a liquid crystal into a liquid crystal cell, the injection inlet is closed with a sealing material such as a resin. The sealing intends to prevent entering of ionic substances and to improve a moisture resistance.
A sealing for the nematic liquid crystal is generally conducted such that after injecting a liquid crystal, substrates are pressed from both sides up to a thickness of a liquid crystal cell, and the liquid crystal excessively injected in the liquid crystal cell is pushed out. When the pushing of the liquid crystal cell is stopped in a state that a sealing material contacts the injection inlet, the liquid crystal cell is inflated. Accordingly, the sealing material is sucked and spontaneously advances into an inside of the injection inlet. Subsequently, the sealing material is cured to complete the sealing.
However, since the ferroelectric liquid crystal has a layer structure which is easily broken by pressure or the like, as being different from the case of the nematic liquid crystal, it is impossible to push the liquid crystal cell as described above. Therefore, in the sealing of the ferroelectric liquid crystal device, as the sealing material does not advance into inside of the injection inlet, the injection inlet is closed by covering the sealing material from outside. In this case, however, the sealing material and the substrate are merely contacted, so that the sealing material easily separates from the inlet. Ionic substances and moisture easily enter or permeate from the gap. Thus, reliability of the device cannot be obtained.
Further, a spherical spacer using a material such as silica or plastics is employed to maintain at a constant interval the substrates which hold a liquid crystal used in a liquid crystal display unit. However, such a spacer has a problem in uniformity in scattering the same on the substrate. For example, it is required for the spacers to be uniformly distributed one by one in a scattering liquid, but selection of a solvent and scattering technique therefor are difficult. Even if the spacers can be uniformly scattered on the substrates, since the spacers move when liquid crystal is injected, the spacers are localized in the liquid crystal cell to have ununiformly therein. The ununiform presence of the spacers causes an irregular display, and a pressure to a substrate surface causes disorder in orientation of liquid crystal or layer structure.
To overcome this problem, it is required to use a spacer which does not move at injection of the liquid crystal. However, in a method for fixing the spacers on the substrates by using a material which has an adhesiveness, the type of a solvent selected at scattering the spacers is limited. In addition, orientation disorder tends to occur around the adhesive material.